<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>测试带属性的自定义标签</title>
</head>
<body>
  <form action="server.jsp" method="post">
    <input type="text" name="username" placeholder="用户名">
    <input type="submit" value="提交">
  </form>
</body>
</html>